This puts a halt to current plans for a massive 1700-mile pipeline that would have allowed some of the world’s dirtiest oil to travel from Canada’s tar sands through America’s heartland — jeopardizing our water, our air and our climate.

Six months ago the pipeline project was considered a foregone conclusion. Today — against all odds — the project has been rejected. That is a heroic political shift, which is the result of massive grassroots opposition that spanned from First Nations in Alberta to farmers in Nebraska.

By sending letters, making calls, protesting in front of the White House and standing up at “Obama for America” offices, the movement against the Keystone XL pipeline has demonstrated what grassroots activism is all about — and what it really takes to make change in this country.

When organizing started against the Keystone pipeline there were two main goals: stop the pipeline, and reignite the climate movement, which had been deflated by disappointments from Copenhagen to Congress. I would say that in just a few months we are well on our way to achieving both goals.

As Bill McKibben, one of the lead visionaries behind the tar sands protests, said in November, when the pipeline was first delayed:

It’s important to understand how unlikely this victory is… A done deal has come spectacularly undone… The American people spoke loudly about climate change and the president responded. There have been few even partial victories about global warming in recent years so that makes this an important day.

McKibben’s words are truer today than they were in November. We have seen little from the administration on climate and energy that we can be enthusiastic about, and this is definitely something to be unanimously proud of.

It has been incredible to watch the movement against the Keystone pipeline come to life. In September, 1,253 people were arrested in a peaceful sit-in at the White House expressing resounding opposition to the pipeline project in one of the largest acts of civil disobedience the environmental movement has ever seen. Since then, droves of protesters, including high-end campaign donors, have confronted President Obama at one public speaking event after another. In November, the opposition grew when more than 12,000 people joined in peaceful protest back in DC, linking hands in several concentric circles around the White House.

Many are wondering what the political realities are to the pipeline rejection. The State Department is allowing Transcanada, the company behind the pipeline, to pitch an alternative route for the pipeline through Nebraska. This re-application process would likely put the project back to the drawing board.

As Frances Beinecke, Executive Director of NRDC, put it in an email blast this afternoon:

[B]ecause Big Oil lost, this is not the end of the fight. This is the beginning of the real battle for America’s energy future…That battle will be fought in Congress, where Representatives who’ve collected $12 million from the oil & gas industry over the past two years are sure to try to raise Keystone from the dead . . . it will be fought in British Columbia, where the oil giants want to ram a tar sands pipeline and supertanker traffic through the heart of the Spirit Bear’s coastal rainforest home . . . it will be fought in the Polar Bear Seas, where the Interior Department has given tentative approval for Shell to begin drilling this summer…

If the last few months have shown us anything, it’s that we’ve stopped the project once and we’ll stop it again. Yes, we will need to continue to ensure that President Obama feels the full weight of our opposition and keeps the Keystone XL pipeline off the map forever. But make no mistake, today is a day to come together to celebrate in the exact same way we came together to fight Keystone over the past couple of months, because celebrating our success is a critical part of fueling our work. That should neither minimize nor obscure the reality that if we want a clean energy future, which stops extreme energy projects like the Keystone XL, we’re going to have to keep fighting together for the long haul.

What an incredible sign for the start of this New Year. Let’s make sure that this success begets even more success in our work to protect forests, their inhabitants and our climate.